Should I move the furnace upstairs to help cool the 2nd story?

Question

My wife and I live in a two story, 1400 sqft home. Recently, our 24 year old HVAC system died on us and we've been recommended by three different independent repair guys to replace the system rather than fix it since the brand that was installed is not that great to begin with. Since this is what we have come to terms with we want to install the right system for our house. One of the issues we always had before which I know most two story homeowners have is the inability to effectively cool down the 2nd story. Currently, the attic has no attic fans. We've had three A/C installers come out to quote us a new system and as to be expected, all came up with a different solution.

The first one (local contractor) was the cheapest and most basic which was to simply replace our current condenser unit, and forced air unit with new Trane models, 13 seer, 3 ton. This was going to be $6300 out the door.

The second contractor (EconoAir through Costco) offered a package that includes replacing the forced air and condenser, but also moving the furnace to the upstairs in our attic, replacing all the ducting with brand new ones, running new gas and electrical, replacing all the registers in the house, installing an attic ladder and relocating the opening to the attic. The brand they use is Lennox and the installer seemed to think moving the furnace to the attic would definitely solve our 2nd story heat issue because the return would be up there and it would be easier for the cool air to move about upstairs. They want about $13K for this system. The package details include, "High performance coil system, oversized suction and liquid drier to clean up a/c system, honeywell prestige flat screen thermostat, complete accoustical sound with oversized returns, Merv 16 air purifier system, complete new plenum system, new free flow high velocity bar type or curve blade registers, all metal wrapped in a commercial fsk wrap, oversized feeders hardwired at the furnace w/ new breakers, new high voltage disconnect w/ new breaker and oversized main feeder, accoustical sound technology for compressor, voltage booster, new stainless steel gas lines installed w new shut off valve, new b-vent cap with collar, install new bacteriostatic, oversized, energy efficient mylar duct system with air balance."

The third contractor offered a package that would replace the condenser with a 15 seer condenser, 3 ton unit (Trane) and would keep it downstairs (though they were willing to move up stairs for $3500), put in an "air accelerator" in the ducts in the attic that would basically help to pull up the cool air from downstairs, as well as an attic fan. Their system would cost out the door about $8600. They also offer lifetime warranty on labor for their system.

-- Basically what I'm trying to figure out is what is the best option for our home to get a new system installed that will sufficiently cool the 2nd story. We plan on being in the house at least another 5 years or so.

Answer 1

I would only place the unit in the attic if it was a second unit and it avoided ducts running up and down walls. With an attic unit, you have to worry about a clog in the condensate line causing a leak in your ceiling. Access is frequently more difficult and requires a trip through your entire home. As tabun mentioned, it's noisier. You'd also need to run power and refrigerant lines up there, which won't be cheap. You also need to worry about insulating the unit and all ducts since the HVAC will likely be in uninsulated space.

Replacing duct work will be a huge job without a lot of reward unless the ducts are easy to access. They will have to pull out drywall all over the place to access the lines.

The best solution would be a couple dampers that you can adjust each season to direct air either upstairs or downstairs. You'll need one installed on each outflow from the HVAC, but the line to the attic is frequently a single trunk going up the wall. You also need to make sure your return upstairs is working well. My personal solution has been to replace my return grilles with the hinged style that supports a filter, and then to leave the filter out of the return that needs more heating or cooling.

The air accelerator would help (make sure it only activates during the AC mode) and be a decent option if you can't use dampers on the vents to the first floor, but otherwise, it's one more thing that can break and I'm a fan of keeping things simple. You may also want to see if they have a system that supports two thermostats and electronically controlled dampers which would cut down on some of the extreme temperature swings you likely have upstairs.

Answer 2

From my experience, just some points to look out for.

I think the best location really has more to do with where there is the most room. Also, if the bedrooms are upstairs a system in the attic can be noisy, and if the runs are short the ducts themselves can be noisy.

If it is not in the way in the basement, I would leave it there, and probably add some insulation to the attic.

The attic fan is nice in areas where the nights are cool, and that seems to be your case, but a lot of people just leave the A/C on, so depends on your preference. They are also a challenge to thermally isolate when not in use -- not sure if they work out net beneficial, or if leaving the A/C on is actually better.